Series-parallel system of control for tapped-field motors.



F. E. CASE. SYSTEM OF CONTROL FOR TAPPED FIELD MOTORS- APPLICATION HIIED MAR. 24, I915.

SERIES PARALLEL "1,262,373.-

Patented Apr. 23,1918. 1 .2 3.45 e 7ss 10 Figi' v I Witnesses; I

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' tion.

' Ties-parallel system NITED. STATES PATENT OFFICE.

FRANK E. CASE, OF

SCHENECTADY, NEW YOR'K, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK;

- sEnIEs-rmaLLnL SYSTEM or common roe TAPPED-FIELD rio'rons.

Specification of Letters Patent. 7 Patented Apr. 23, 1918.

Application mes March 24, 1915. Serial No. 16,746.

To all whom it may concern:

l 3e it known that I, FRANK 'E. (less, a citlzen of the United States, residing at Schenectady, county of Schenectady, State ofNeW York, have'invented certain new and useful Improvements in Series-Parallel Systemsof Control for Tapped-Field Motors, of which the following is a specificalMy invention relates to the control of series wound electric motors and has for its object the rovision of means whereby a plurality 0 such motors may be operated and controlled in an eflicient manner.

, My invention relates particularly to' aseof control for a plurality'of series wound motors and provides a sequence of connections utllizlng interme- 'diate taps in the field windings for securlng additional running connections and a greater range of speed control, by weakenx More specifically my invention provides certo parallel relation, as it tween the two armatures to avoid dropping back to bridging or unting conthe transition from series is accomplished by tain tapped field nections whereby on the motors. and withthe motor circuit.

out opening difficulty has been experienced Her'etofore in securing proper connections for tapped transition from series is necessary to pass from the tapped field series arrangement to field motors during the first parallel arrangement with full field, and it is necessary during this transition, in order to eliminatethe sag in torque,

ries position. M invention successfully overcomes this di 'culty and by means of the connections which I provide, the torque on the various motors is maintained during transition.

In, my system of control as illustrated, a

pair, of motors with dividedfield windings are" reversely connected in series with each jother and with a starting resistance; bythe term reversely connected in series, I mean that the motors are connected in series, with the fields of the two motors connected be the drawings. After starting the motors, the resistance is gradually cut out and a bridge connection established between intermediate taps in the field windings of the the field strength of the various motors.

.sent respectively the the full field seas illustrated in two motors until the motorsa'reconnected v in arallel. This connection weakens the field strength of the two motors giving a higher running speed.

he portions of the field windings shunted by the bridge connection are then utilized to establish a full field parallel relation of the two motors withpart of the resistance in series with each motor. -The bridge connection left in full field parallel relation with resistance in each circuit. This resistance is then gradually cut out and finally the field of each motor is tapped at an intermediate point to produce weakened fields for higher speed parallel operation.

In passing from series to parallel it will be seen that the full field is introduced without an intervening time interval and the possibility of a sag in torque is therefore eliminated.

A better understanding of my invention will be had by referring to the accompanying drawing in which Figure 1 illustrates diagrammatically a pair of motors and a controller by means of which the various steps in my control s stem are accomplished; Figs. 2 to 7 show t e successive series connections; Fig. 8 shows the connection established preparatory to shifting the motors from series 'to parallel and Figs. 9 to 12 show the successive parallel connections.

Referring to the drawing, A and A reprearmatures wound motors each having its field. divided into two parts as at F, F, and F F respectively. Sections of starting resistance r, r '1' and r are provided for varying the speed of the motors. C is a controller, which as shown is of the ordinary drum type provided with contact fingers a. to is and'coopcrating contact segments arranged to provide the desired motor connections. rious running positions are indicated by dotted lines of which 1 to 6 are the series positions; 6 indicates the transition step and 7 to 10 are the parallel positions.

The first controller finger a is connected through the lead Tto the source of current. When the controller C is movcdto the first running position indicated by the dotted line 1 the motors are connected to thesource of current in series with each othefi and with the resistances 734 ,.1' and rtas shown in of two series The va- As'the controller is moved from position 1 to position 2 the section of resistance r is short-circuited and as the controller is progressively moved through positions 3, 4 and 5 the other sections of resistance are shortcircuited as shown in Figs. 3 to 6 inclusive and finally as the controller is moved for- Ward to position 6 a bridge connection is established between the intermediate points in the field windings of the two motors and the connection between resistances r and r is broken. This arrangement, illustrated in Fig. 7, gives a weakened field condition. The dotted line 6 indicates the transition step where the disconnected portions of the motor fields are utilized to establish a full field parallel arran ement of the motors as shown in Fig. 8 wit out breaking the bridge connection of the last series position ,and without opening the motor circuit.

As the controller is advanced to position 7, the tapped field bridging connection is broken and the motors are then in full field parallel arrangement with resistance in series with each motor as in Fig. 9.

The resistances in the two motor circuits are then gradually cut out as the controller is moved through positions 8 and 9, as illustrated in Figs. 10 and 11; and finally in position 10 of the controller a portion of each motor field is tapped out as illustrated in Fig. 12.

It will be seen that by my invention the transition of plurality of tapped field motors from series to cessfully accomplishe without breaking the motor circuits and Without unbalancing of the load on the motors.

I have set forth above, the principle of operation of my invention and have described and illustrated it as embodied in a specific manner, but it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the spirit of my invention, the scope of which is set forth in the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. The series-parallel method of control for a plurality of series motors which consists in connecting the motors series bridging across intermediate points in the fields, and then making the parallel connection with the bridge connection maintained.

2. Th series-parallel method of control for a plurality of series motors which consists in connecting the motors in series to a source of supply, shunting a portion of the field of each motor, and then connecting the motors in parallel with full field with the connection of the motors to the source of'supply maintained during the transition from the series to the parallel connection. 1

3. The series-parallel method of control arallel relation is sucfor a plurality of series motors which consists in connecting the motors in series to a source of supply, disconnecting a portion of the field of each motor while maintaining the connection of the motors to the source of supply, and then connecting the motors in parallel with full field without having opened the connection of the motors to the source of supply.

4. The series-parallel method of control for a plurality of series motors which consists in connectin the motors in series with full field, weakenm the motor fields until making the paralle connection and then pionnecting the motors in parallel with full 5. The series-parallel method of control for a plurality of series motors which consists in connecting the motors in series with full field, establishing a brid connection between the motors at interme iate points in the fields, connecting the motors in parallel with the bridge connection maintained, and finall breaking the bridge connection.

6. The rice-parallel method of control for a plura ity of series motors which consists in connecting the motors in series with fulLfield, weakenin the motor fields until making the paralle connection, and then connecting the motors in parallel with full field without having opened the motor circuit.

7. The series-parallel method of control for a plurality of series motors which consists in connectin the motors in series with full field, weakening the fields b v bridging acrom intermediate points in the fields before connecting the motors in parallel and finally breaking the bridge connection after.

the full field parallel connection of the motors is made.

8. The series-parallel method of control for a plurality of series motors which opensists in connecting the motors reverseliy in series with full field, weakening the fiel s by bridging across intermediate points in the fields before connectin the motors in parallel, and finally brea in the bridge connection after the full field parallel, connection of the motors is made. I

9. The series-parallel method (1'', control for a plurality of series motors which consists in connecting the motors in series with full field, weakening the fields byv bridging across intermediate points in the fields until making the arallel connection'and finally connecting t e motors in full field parallel nee-3,373

in'each motor circuit, and finally breaking the shunt connection.

11. The series-parallel method of control for a plurality of series motors which consists in connecting the motors in series With a starting resistance, short circuiting the resistance, bridging across intermediate points in the fields and open-circuiting the resistance, connecting the motors in parallel with a portion of the resistance in each inotor circuit without having opened the motor circuit, and finally breaking the bridge connection.

12. The 'seriesparallel method of control for a plurality of series motors which con sists in connecting the motors in series with. full field, weakening the fields by shunting portions of the fields end open eircuiting the shunted portions, connecting the motors in parallel with the shunted portions of the fields reconnected in circuit, and finally opening the shunt circuit.

1.3. The series-parallel method of control for a plurality of series motors which consists in connect-in the motors in series With full field, weakening the fields until melting the parallel connection, connecting the motors in parallel with full field, and finally weakening the fields. i

14. The method of control for a plurality of series motors which consists in connecting the motors in with connecting a, portion of the note. o e tor until making the parallel co connecting the motors in parell portions of the fields reconnectec and finally disconnecting a portion of field of each motor.

15. The combination with e plum series motors of a series-parallel therefor having means whereby the r are first connected in series with T" then the field of each mot-or Wear. the parallel connection is made an the motors are connected in, paral it full field,

16. The con hination who so ies motors of e eerie. i therefor havingni-eans whereby are first connectecl in series wit then 1r bridge connection establishe the motors at intermediate points fields, nexta full field parallel canoe the motors is made with the bridge o tion maintained and finally the bridg nection is broken.

In witness whereof, l have hereunto set my hand this 23rd. day of arch,

- FRANK E, i.

Witnesses:

BE JAMIN EtULL, HELEN Onroro, 

